Antifreeze circulation through engine

[Drcoffee]

What if i ran boat without drain plugs for approx 5 mins in manifold ?
I was focused what I’ve found in my rubber hose , it was a little bit crunchy when squeezed, I always drain via drain plug

Where is that rust coming from? Thats the exhaust?

 

[Kubaat3lover]

From port side from thermostat (right side If looking toward the engine) then it goes on o the bottom side of exhaust manifold

 

[Lou C]

Is that from the engine block or the exhaust manifold? Either way that’s a LOT of rust flakes….I’ve been boating in salt water close to 20 years with the same boat and engine and never seen that many rust flakes when I winterized it. Salt water use? If from the block I’d remove the thermostat housing to check the bottom of the intake manifold because they sometimes rot out right under the thermostat and that will put water right in the cam valley right into the motor oil. If it’s from the exhaust manifold I’d think about replacing it, that much in terms of rust flakes means the cast iron is getting thin. Rotted manifolds will put water in a cylinder and rust exhaust valves.
This is why I say that cast iron inboards should be closed cooled!

 

[Lou C]

Ah just saw your post, if that’s in the hose leading to the manifold from the thermostat housing I’d remove the housing and see what’s going on in there. If the intake looks really rotted right under the thermostat you may need to replace it. There is a water passage at the front of the intake manifold so hot water from each cyl head can exit via the stat housing to the exhaust manifolds.

 

[Kubaat3lover]

Fresh water, lake , Termostat replaced A year ago and it was pretty fine I don’t know why is that junk came from, I will drop manifolds tomorrow for the winter

 

[Bondo]

I just forgot to screw the blue plug in after cleaning this junk in hose , boat ran No more than 5 mins @ idle

Oh,..... Ya oughta be Ok,.....